This invention is generally directed to guidewires and guiding members for dilatation catheters which are suitable for percutaneous transluminal coronary angioplasty (PTCA).
In typical PTCA procedures a dilatation catheter having an inflatable, relatively inelastic balloon on the distal end thereof is advanced through a patient's arterial system until the balloon crosses the atherosclerotic lesion to be dilated. The balloon is inflated to a predetermined size with radiopaque liquid by a syringe-like inflation device mounted on the proximal end of the catheter to dilate the lesion and then it is deflated so that the catheter can be removed and blood flow resumed.
The first step of the procedure is to percutaneously introduce a guiding catheter having a preformed distal tip into the patient's arterial system (e.g.the femoral artery) and advance it therein until the preformed distal tip is seated within the ostium of the patient's appropriate coronary artery. In over-the-wire systems a guidewire is usually preloaded within an inner lumen of the dilatation catheter and both are advanced through the previously positioned guiding catheter to the distal end thereof. The guidewire is first advanced out of the distal tip of the guiding catheter into the patient's coronary artery until the distal end of the guidewire crosses the stenotic region to be dilated. The physician usually shapes the distal end of the guidewire to facilitate guiding it through the patient's tortuous coronary anatomy to the stenotic region. When the guidewire is in the desired position, the dilatation catheter is then advanced out of the guiding catheter over the guidewire until the inflatable balloon on the distal end thereof is positioned across the stenosis. The balloon is inflated one or more times to a relatively high pressure (e.g. up to 8 atmospheres or more) by the inflation device to dilate the stenosis. After the stenosis has been dilated, the balloon is deflated and the catheter is removed.
For a more detailed description of angioplasty procedures and the devices used in such procedures, reference is made to U.S. Pat. No. 4,323,071 (Simpson-Robert); U.S. Pat. No. 4,332,254 (Lundquist); U.S. Pat. No. 4,439,185 (Lundquist); U.S. Pat. No. 4,468,224 (Enzmann et al.); U.S. Pat. No. 4,516,972 (Samson); U.S. Pat. No. 4,538,622 (Samson et al.); and U.S. Pat. No. 4,616,652 (Simpson) which are hereby incorporated herein in their entirety.
Steerable dilatation catheters with built-in or fixed guidewires or guiding elements are frequently used because the deflated profile of such catheters are generally much smaller than conventional dilatation catheters having the same inflated balloon size. Further details of low-profile steerable dilatation catheters may be found in U.S. Pat. No. 4,582,181 (Samson), U.S. Pat. No. 4,771,778 (Mar), and U.S. Pat. No. 4,793,350 (Mar et al.) and copending application Ser. No. 287,772, filed Dec. 21, 1988, which are hereby incorporated in their entirety by reference thereto. The low profile and improved pushability of these catheters allows them to cross tighter lesions and to be advanced much deeper into the patient's coronary anatomy. Moreover, the use of steerable, low-profile dilatation catheters having a built-in guidewire or guiding element shortens the time for angioplasty procedures because there is no need to first advance a guidewire out the distal end of the guiding catheter into the patient's coronary artery and then advance a dilatation catheter over the previously positioned guidewire.
Guiding members and guidewires used in angioplasty procedures generally include an elongated core member with a flexible helical coil secured to the distal extremity of the core member. The core member can extend to the distal end of the coil and be secured thereto or the distal extension of the core element can terminate short of the distal end of the coil and a thin, flat shaping ribbon can extend to the distal end of the coil and be secured by its distal end thereto. In the latter instance the ribbon is secured, usually by soldering or brazing, by its proximal end to the core element. Welding could be employed, but the physical properties in the heat affected zone of the weldment would be reduced to unacceptable levels for the intended uses of the product. Even when low temperature bonding methods such as soldering or brazing are used, the prior art ribbons frequently had limited resistance to torquing.
What has been needed and heretofore unavailable is an improved distal structure for guiding members such as guidewires which has the strength to withstand extensive torquing with little or no loss in flexibility and which can be easily shaped by the physician before inserting the guiding member into the patient. The present invention satisfies this need.